GENERAL OBJECTIVES: Our main goal is to uncover new facts about DNA replication and recombination. Bacteriophage systems are used and our general objective is to isolate replicative and recombinational intermediates which are then studied mainly by electron microscopy. Our earlier work involved the study of purified intermediates; we now wish to take the next step and look at intermediates which have not been purified and which therefore still have their enzymatic machinery intact.